Gate dielectric material influence on DC behavior of MO(I)SHEMT devices operating up to 150 °C

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In this work, the DC behavior of AlGaN/GaN Metal-Insulator-Semiconductor high electron mobility transistors (MO(I)SHEMTs) with two different gate dielectrics (Al 2 O 3 and Si 3 N 4 ) is analyzed through the experimental comparison of their basic and analog parameters. The transistors with Si 3 N 4 insulator are more closely related to the normally-off devices (less negative threshold voltage) and less affected by the short channel effects (better DIBL behavior). Although the devices with Si 3 N 4 layer presented a double conduction, that results in anomalous transconductance behavior, it is more suitable for analog applications since the Al 2 O 3 devices suffer large self-heating. The very high gate leakage of Si 3 N 4 MISHEMT degrades the subthreshold regime, which decreases the transistor efficiency at weak inversion. On the other hand, the devices with Si 3 N 4 insulator present relatively large Early voltage and consequently high intrinsic voltage gain in strong inversion, reaching 84 V/V (38.5 dB). Even at high temperatures the intrinsic voltage gain is practically the same, degrading only 1.5 dB from 25 °C to 150 °C for a long channel device.